Device-to-device (D2D) communication, also referred to as user direct connection communication, means that data can be directly transmitted between devices without an aid of a third party. In D2D transmission, transmit power of a transmitting device directly affects a receive signal level of a receiving device, and further affects performance of a link between the transmitting device and the receiving device. In particular, in dedicated short range communications (DSRC) or an intelligent transport system (ITS), transmit power of a vehicle, which is a special D2D device, also directly affects a coverage area of a safety message, and affects safety of a nearby vehicle.
Therefore, how to enable a transmitting D2D device to appropriately set its transmit power to make actual coverage performance of the transmitting D2D device match expected coverage performance is a problem to be resolved at present.